For many years digital X-ray detectors have been changing classical radiography. The wide variety of newer technologies which have been in use for a long time or are becoming mature enough to be marketed include image enhancement camera systems based of television or CCD cameras, memory foil systems with integrated or external read-out unit, systems with optical coupling of the converter foil to CCDs or CMOS chips, selenium-based detectors with electrostatic readout as well as semiconductor detectors with active readout matrices with direct or indirect conversion of the X-ray radiation.
In particular various innovative semiconductor X-ray detectors for digital X-ray imaging have been under development for some years now, using various technologies to convert the original X-ray image information into a form that can be evaluated to produce electronic images. One option is to initially convert the original image information in an X-ray converter, consisting for example of cesium-iodide, into electromagnetic radiation with a low frequency, and subsequently convert it and store it in a photo-diode matrix into a electrical charge pattern corresponding to the image information. The charge pattern stored latently within the photo diode matrix is then read out and processed further to create the image.
A further technology for example uses semiconductor X-ray converters made of selenium which generate an electrical charge pattern directly which corresponds to the original image information. The latent stored charge pattern in the X-ray converter is then in its turn read out and further processed for image processing.
The conversion layers of these types of semiconductor X-ray detectors, which use X-ray converters based on cesium-iodide, selenium or other materials do not have any complete resistance to external climatic influences, such as for example temperature, humidity or air pressure. Furthermore these types of semiconductor X-ray detectors are sensitive to electromagnetic radiation as well as to any form of electrostatic charge.
Comprehensive precautions therefore need to be taken up when dispatching such semiconductor X-ray detectors. One is to apply waterproof and air-tight layers during manufacturing to protect the X-ray converter layer against external climatic influences. These layers however do not guarantee any complete protection for the expensive sensors. Another precaution is to pack the semiconductor X-ray detectors in a metalized, antistatic, i.e. opaque and frequently also partly evacuated plastic foil. The plastic foil is tightly hermetically sealed or sealed in some other way to give this protection.